There is only 1 way to isolate a room. If you use a millstone, you can place the mill shaft to its bottom (place all other shafts under the floor and behind the wall). If you use a helve hammer, it is not possible. I put the helve hammer in the forge to a small room behind wide doors that are constantly open. This creates the illusion of a single room, but the main part of the forge is warm. There is 1 mod that solves the problem of room isolation and now it is updated. https://mods.vintagestory.at/axleinblocks But in the past it was not updated every time and this was a problem for us.